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Hydraulic valves are manufactured in a variety of styles to function in different applications. Valves are used to manipulate the flow of hydraulic fluid within a hydraulic circuit. Valves can be either mechanically or electronically operated. Generally, a valve is composed of a spool that is shifted with springs or magnets. The valve spool contains small openings that allow fluid to flow from one circuit to another.


Fluid power systems consist of multiple components that work together or in sequence to perform some action or work. People well versed in fluid power circuit and system design may purchase individual components and assemble them into a fluid power systems themselves. However, many fluid power systems are designed by distributors, consultants, and other fluid power professionals who may provide the system in whole or in part.

A hydraulic control valve should be selected based upon both the highest flow rate the valve is expected to achieve and the system's maximum pressures. Be sure to consider the effects of each hydraulic component in the system when selecting a valve.


A selector valve allows one power source to operate two separate circuits independently. It can also be used to transfer two different flows or pressures to one circuit.

Relief Valves are used to transfer fluid back to the tank if and when the system pressure exceeds the relief valve's pressure setting. Relief valve are almost always adjustable, but generally come preset.

Flow dividers split flow from one source and divide it proportionally between two or more components in a circuit. A flow divider can be used to allow two cylinders to extend at the same time or two motors to rotate at the same speed.


Pressure compensated flow controls adjust for pressure changes in the circuit and maintain a constant output flow. A pressure compensated valve can also be used to prevent excessive heat build-up by maintaining an exhaust flow.


A Ball valve is used in fluid power applications where a complete manual shut-off is required. The quarter turn operation offers a quick way to isolate a portion of a system. Handles of the ball valve should be oriented to indicate the internal position of the valves. When the handle is in-line with ports it is in the open position and when the handle is perpendicular to the ports it is in the closed position.

In-line Flow Control Valves

An in-line valve can perform a variety of functions to help a system operate properly. Needle and flow controls adjust the amount of fluid that can pass through the valves and are able to limit the speed of a cylinder or motor.